Low end systems, which are small computer systems in the order of the size of a desk, must utilize all available memory and engine cards to control system design costs. The logic heart of these systems are large functional planar boards which provide the lowest cost packaging approach from the standpoint of design, build, and test service. These boards provide the necessary memory, logic, and computing functions for a low end computer system and they are larger in size and have more components mounted on a single plane compared to conventional printed circuit cards. Also, planar boards are interconnected at their planar surface whereas printed circuit cards are generally interconnected along an edge which connects their planar surfaces.
Heretofore, these planar boards have been connected to the computer system by cables and they were fastened to the machine at a location remote from the card-on-board assembly. This required a costly assembly procedure. Also, the removal of planar boards for replacement or interchanging proved to be cumbersome, time consuming, and costly. The intricate cabling had to be disconnected and the board unscrewed from the machine frame which required generally about one hour. It became evident that what was needed was a totally integrated package at the lowest possible total system cost and wherein planar boards could be easily and quickly inserted or extracted.